Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/12—Powdering or granulating
  • C08J3/122—Pulverisation by spraying
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F261/00—Macromolecular compounds obtained by polymerising monomers on to polymers of oxygen-containing monomers as defined in group C08F16/00
  • C08F261/02—Macromolecular compounds obtained by polymerising monomers on to polymers of oxygen-containing monomers as defined in group C08F16/00 on to polymers of unsaturated alcohols
  • C08F261/04—Macromolecular compounds obtained by polymerising monomers on to polymers of oxygen-containing monomers as defined in group C08F16/00 on to polymers of unsaturated alcohols on to polymers of vinyl alcohol
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/12—Powdering or granulating
  • C08J3/124—Treatment for improving the free-flowing characteristics
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2331/00—Characterised by the use of copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, or carbonic acid, or of a haloformic acid
  • C08J2331/02—Characterised by the use of omopolymers or copolymers of esters of monocarboxylic acids
  • C08J2331/04—Homopolymers or copolymers of vinyl acetate

Definitions

• Dispersible powders of vinyl acetate/ethylenecopolymers are known. The following requirements have to be met by such a polymer powder: it should be capable of flowing freely, have a long storage life and good dispersibility in water.
• the dispersion obtained with water from the polymer powder should have a minimum film forming temperature of approx. C and its particles should have approximately the same average particle size as those of the initial dispersions.
• the dispersions should also be stable over a longer period of time, i.e., they should have no tendency to sedimentation.
• the polymer powders should be suitable as binding agents for plastics mortars.
• the plasterings made therewith should be free from cracks and resistant to water.
• the present invention provides a process for the preparation of a free-flowing and easily dispersible polymer powder comprising a vinyl acetate-ethylene copolymer, wherein an aqueous dispersion prepared by polymerization of vinyl acetate at an ethylene pressure of up to 100 atmospheres, and in the presence of from 0 to l by weight, calculated on the polymer, of an ionic emulsifier of from to by weight, calculated on the polymer, of at least one polyvinyl alcohol with a degree of saponification of from 80 to 92 mol and a viscosity of the 4 aqueous solution at 20C of from 3 to 35 0F, and ofa free radical initiator, is spray dried, and simultaneously of from 3 to 30 by weight, calculated on the solids content of the aqueous dispersion of finely dispersed aluminium silicate, silica or calcium carbonate having an average particle size of from 0.01 to 0.5 u are introduced in the dry state in the spray tower as anti-caking agents.
• the aqueous vinyl acetate/ethylene copolymer dispersions contain approximately 5 to 40 by weight, calculated on the polymer, of polymerized ethylene. If further monomers are used together with vinyl acetate and ethylene the polymer should, preferably, contain polymerized vinyl acetate in an amount of at least 45 by weight.
• olefinically unsaturated monomers for example vinyl esters of straight chain or branched saturated aliphatic mono-carboxylic acids having 3 to 18 carbon atoms, acrylic, methacrylic, maleic, or fumaric acid esters of straight chain or branched saturated monohydric aliphatic alcohols having 1 to 18 carbon atoms, vinyl chloride, isobutylene or higher oz-mono-olefins having 4 to 12 carbon atoms.
• vinyl acetate and ethylene other suitable monomer combinations are, for example, vinyl acetate/vinyl pivalate/ethylene, vinyl acetate/Z-ethyl-hexanoic acid vinyl ester/ethylene, vinyl acetate/methyl methacrylate/ethylene and vinyl acetate/vinyl chloride/ethy lene.
• Preferable are monomer combinations having a minimum film formation temperature of the corresponding aqueous dispersions of approximately 0C.
• monomers mentioned also other monomers having a stabilizing action can be used, for example, the sodium salt of vinyl sulfonic acid, monomers containing carboxylic groups, such as acrylic, methacrylic, crotonic, or itaconic acid or moiioesters of maleic acid, the alcohol components of which can contain 1 to 18 carbon atoms, in a concentration of up to 5 by weight, calculated on the total polymer.
• monomers with two or more unsaturated double bonds can be used as crossJinking components, such as diallyl maleate, diallyl phthalate, triallyl cyanurate, tetraallyl oxyethane or adipic acid divinyl ester.
• the aqueous vinyl acetate/ethylene dispersions can be prepared in various ways at ethylene pressures of up to approximately 100 atmospheres, preferably from 10 to 60 atmospheres.
• a batch-process can be used in which the total amount of monomer is emulsified in the aqueous medium before the beginning of polymerization.
• a monomer feed process is used in which at a certain ethylene pressure, vinyl acetate or mixtures of vinyl acetate and other olefinically unsaturated monomers are added continuously to an aqueous medium.
• the ethylene pressure can be kept constant during the whole feed period, the process can, however, also be carried out at increasing or decreasing pressure.
• polyvinyl alcohols As protective colloids for the preparation of the vinyl acetate/ethylene dispersions one or more polyvinyl alcohols are used having a degree of saponification of from to 92 mol preferably from 86 to 89 mol and a viscosity of the 4 aqueous solution at 20C of from 3 to 35 cP.
• the quantity of polyvinyl alcohol, calculated on the polymer, is from 5 to 20 by weight, preferably from 10 to 15 by weight.
• 50 to 90 of the protective colloid used is advantageously contained at the beginning of the polymerization in the aqueous medium and 10 to 50 is added to the finished dispersion in the form of an aqueous solution.
• polyvinyl alcohols used as protective colloid up to l calculated on the polymer of ionic emulsifiers can be used, preferably emulsifiers of the alkyl sulfate type having 10 to 16 carbon atoms.
• the pH of the dispersion medium is adjusted in the range of 4 to 7.5.
• a suitable buffer such as for example sodium acetate, sodium bicarbonate or sodium phosphate can be added.
• the polymerization temperature is between 20 and C, preferably between 50 and 70C.
• free radical initiators are used.
• water-soluble peroxo compounds such as ammonium, sodium or potassium persulfate, hydrogen peroxide, or perborates
• monomer-soluble compounds such as for example t-butyl hydroperoxide or cumene hydroperoxide, alone or also in the form of redox systems.
• the individual components can be added to the dispersion medium either before the polymerization or at the same time as the monomers or separately during polymerization.
• the solids content of the vinyl acetate/ethylene dispersions prepared in this way is approximately 30 to 60 by weight.
• dispersions are prepared with a solids content of approximately 40 to 60 by weight.
• a solids content, suitable for the spray drying, of approximately 30 to 45 by weight is set by adding water or an aqueous polyvinyl alcohol solution.
• aqueous vinyl acetate-ethylene dispersions are converted by spray drying into dispersible polymer powders
• dispersions with a minimum film forming temperature of approximately C it has proved necessary to add fine particle inorganic substances as anti-caking agents during spray drying. If these admixtures are not used the dispersible powders do not have a sufficient storage life.
• Suitable inorganic admixtures are silica, calcium carbonates or aluminium silicates with an average particle size of 0.01 to 0.5 1.1..
• Silica or aluminium silicates have proved especially advantageous as anti-caking agents.
• Polymer powders of particularly high storage stability are obtained when the anti-caking agents are contained in the polymer powder in a quantity of 4 to by weight, calculated on the solids content of the aqueous dispersion. The finer the particles of the anti-caking agents are, the less is the quantity necessary for stabilization.
• the anti-caking agent is metered into the spray tower in dry form at the same time as, but separately from, the aqueous dispersion, whereby hardly any deposit forms on the walls of the dryer";
• the vinyl acetate/ethylene copolymer powders of the invention are free flowing, their storage life is also good at elevated temperature. They can be dispersed in water within a few seconds forming creamy aqueous dispersions having a constant viscosity and good shelf life.
• the size of the latex particles of the dispersions obtained from the polymer powders practically corresponds to the particle size of the latex particles of the initial dispersions.
• the polymer powders have as good an alkali stability as the initial aqueous dispersions.
• the vinyl acetate/ethylene copolymer powders of the invention are exceptionally suitable for the preparation of glues, adhesives and paints.
• a preferred and especially suitable application is as binding agent in plastics mortars.
• Mortars of this type are prepared by intensive mixing of mineral aggregates of different grain sizes with the vinyl acetate/ethylene polymer powders of the invention with final addition of water. Plasterings prepared with plastics mortars containing these powders are, surprisingly, free from cracks and very water resistant.
• EXAMPLE I Preparation of the vinyl acetate/ethylene copolymer dispersion Into a 30 l autoclave with a temperature regulating device and stirring apparatus there was introduced a solution adjusted to a pH of 5.0 of 7 g of sodium lauryl sulfate, 500 g of polyvinyl alcohol having a viscosity of the 4 aqueous solution at 20C of approximately 18 c?
• ethylene was added up to a pressure of 20 atmospheres.
• 68% of vinyl acetate and a solution of 14 g of ammonium persulfate in 600 g of water were metered in over a period of 8 hours at an internal temperature of 60C and an ethylene pressure of 20 atmospheres.
• a solution of4 g of ammonium persulfate in 150 g of water was added to the mixture and the whole was heated for 1.5 hours at an internal temperature of C.
• the ethylene supply was stopped and the dispersion cooled to room temperature.
• the temperature of the drying gas was 90 to 91C at the tower entrance and 58 to 62C in the cyclone separator.
• the throughput of the spraying air for the product nozzle was 20 kg/h, the pressure in front of the nozzle was 5 atmospheres gage, the temperature was 23C.
• anti-caking agents were sprayed in the dry state.
• Example l The vinyl acetate/ethylene copolymer dispersion prepared in Example l,( 1 could be sprayed perfectly over a period of several days.
• the product discharge over tower cone, cyclone separator and collecting vessels took place by itself, it was not neccessary to tap these parts of the apparatus.
• the tower walls were covered only slightly with dryproduct after spray drying of over a week. This deposit could be easily blown off and had the same properties as the free flowing powder obtained in the collecting vessels.
• Using various anticaking agents in different quantities free flowing vinyl acetate ethylene copolymer powders were prepared. The properties of 2 powders are given below.
• a synthetic silica having an SiO -content of 93 a surface area according to BET of 230 m /g and an average particle size of approx. 0.018 p. was used in a quantity of 6 by weight, calculated on the solids content of the aqueous dispersion.
• the powder was very free flowing and had an excellent storage life. After a 24 hour storage at 50C under a load of 200 g/cm the powder could be loosened easily.
• the bulk weight was 40 g/l, the volume after vibration 83 the weight after stamping 49 g/l.
• the powder could be stirred with water within a few minutes to give a 50 aqueous dispersion.
• the viscosity of the dispersion was 160 Ps (Epprecht-Rheometer DI"), the minimum film forming temperature approx. 0C, the size of b.
• As anti-caking agent an aluminium silicate having a SiO content of approx. 82 and an Al O content of approx. 12 and an average particle size of approx. 0.5 p. was used in a quantity of 14 by weight, calculated on the solids content of the aqueous dispersion.
• the powder was very free flowing, the storage life was excellent. After 24 hours of storage at 50C and under a load of 200 g/cm the powder could be loosened easily.
• the bulk weight was 47 g/l, the volume after vibration was 82 the weight after stamping was 58 g/l.
• the dispersion obtainable within a few minutes with water had a viscosity of 60 Ps (Epprecht-Rheometer C II), the minimum film forming temperature was approx. 0C, the size of the latex particles approx. 0.8 p..
• the powder could be worked excellently according to the given instructions 1 to 4 in the following table to mortars yielding crack-free and water resistant plasterings.
• Vinyl acetate ethylene copolymer powder 127 g 120 g 180 g l84 g Sodium polyphosphate solution l0 in water 2 g 2 g 13 g Defoamer Nopco 8034 2 g l g 2 g 2 g Titanium dioxide rutile type RN 56 10 g 44 g 65 g 50 g Calcite, size of grain l0-30 p: 490 g natural Mg/Al-silicate/ size of grain approx.
• the polymer powder was also suitable for preparing glues and adhesives, for example for sticking PVC- furniture foils onto chip boards and as binding agents for pigments, for example for the preparation of paints.
• the vinyl acetate/ethylene copolymer dispersion was prepared as in Example I, 1, however, instead of the aqueous polymerization mixture used in said example, an aqueous solution of 820 g of polyvinyl alcohol having a viscosity of the 4 aqueous solution at 20C of approximately 4 cP and a degree of saponification of approximately 88 mol 15.3 g of anhydrous sodium acetate, 12.5 g of sodium disulfite and 7,700 g of water was used. The process was carried out as in Example I, 1. After polymerization and cooling a solution of 220 g of a polyvinyl alcohol having a viscosity of the 4 aqueous solution at 20C of approximately 4 c?
• EXAMPLEIIl Preparation of the vinyl acetate/ethylene copolymer dispersion
• the dispersion was prepared as in Example 1, (1); however, instead of the aqueous polymerization mixture used there, an aqueous solution of 4 g of sodium lauryl sulfate, 650 g of polyvinyl alcohol having a viscosity of the 4 aqueous solution at 20C of approx. 8 c? and a degree of saponification of approx. 88 mol 15.3 g of anhydrous sodium acetate, 12.5 g of sodium disulfite and 7,600 g of water was used.
• the process was carried out as in Example I, (1), however the polymerization was carried out at an ethylene pressure of 15 atmospheres.
• the vinyl acetate/ethylene copolymer dispersion obtained after dilution to a solids content of 40% had the following properties:
• vicosity'of the 50 aqueous dispersion prepared from the powder was 1 10 Ps, the minimum fim forming temperature was approx. 0C, the size of the latex particles was 0.9 ,u.
• mortars were prepared using this polymer powder. The plasterings made therefrom were crack-free and waterresistant.
• EXAMPLE IV I Preparation of a vinyl acetate/vinyl chloride/ethylene-terpolymer dispersion The process was carried out as in Example I, 1, however, instead of vinyl acetate a mixture of 9 parts by weight of vinyl acetate and 1 part by weight of vinyl chloride was used and the ethylene pressure was raised to 30 atmospheres.
• the aqueous dispersion had the following properties:
• Viscosity Epprecht-Rheometer D III: 78 Ps Average size of the latex particles: 0.8 p.
• the powder was free flowing and stable on storage, it could be easily stirred with water to a stable, creamy 50 aqueous dispersion and plasterings produced with plastics mortars containing the'powder showed no cracks and were stable when stored under water.
• a process for the preparation of a free-flowing and easily dispersible polymer powder comprising a copolymer of vinyl acetate and ethylene and optionally at least one further olefinically unsaturated monomer, wherein said copolymer is dried in a tower as an aqueous dispersion prepared by copolymerization of the monomers in an aqueous system at an ethylene pressure of up to 100 atmospheres and in the presence of from 0 to l by weight, calculated on the polymer, of an ionic emulsifier, the improvement comprising adding to said aqueous system from 5 to 20 by weight, calculated on the polymer, of at least one polyvinyl alcohol with a degree of saponification of from to 92 mol and a viscosity of a 4 aqueous solution of said polyvinyl alcohol at 20C from 3 to 35 0?, said copolymerization being in the presence of a free radical initiator in said aqueous system, and spray drying said aqueous dis
• said further olefinically unsaturated monomer is a vinyl ester of a linear or branched saturated aliphatic monocarboxylic acid having 3 to 18 carbon atoms, an arcylic,
• % by weight of the polyvinyl alcohol is added to the aqueous system before polymerization and 10 to 50 by weight of the polyvinyl alcohol is added to the aqueous dispersion after polymerization.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Adhesives Or Adhesive Processes (AREA)

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